The present invention relates generally to a cutting torch, and more particularly to a gas cutting torch having a mixing chamber and a diffuser for mixing preheat oxygen and preheat fuel. A typical cutting torch generates a preheat flame that initially heats a workpiece to a desired kindling temperature and a separate cutting oxygen stream that reacts with the heated ferrous material, and thus, initiates the cutting process. Steel, an exemplary workpiece material, has a kindling temperature of approximately 1800xc2x0 F. and a melting temperature of approximately 2700xc2x0 F. The preheat flame is produced from the combustion of a mixture of gaseous fuel (i.e, liquid petroleum, natural gas, or acetylene) and oxygen flowing from the tip of the torch. The cutting stream is generated from a separate flow of cutting oxygen that is discharged from the torch at a relatively higher flow rate than the preheat gas mixture.
Existing cutting torches have mixing apparatus that typically include a removable nozzle mixer and venturi-type diffuser for combining the preheat oxygen and fuel. Current torch designs locate the removable mixer and diffuser in the torch head or in a mixing tube upstream of the torch head. Typically, existing torch designs with a removable mixer and diffuser require either elastomeric seals (e.g., O-rings) or metal-to-metal seals between mating surfaces. Frequently, elastomeric seals fail when exposed to sustained backfires or high heat from prolonged operation of the torch. Metal-to-metal seals require high tolerance fittings that require complex machining and high installation torque making the manufacture, installation, and removal of the torch components more time consuming and costly. Also, in existing designs the mixer and diffuser are angled in the torch head with respect to the gas supply tubes to allow installation and removal of the mixer and diffuser from the head. This angled arrangement typically results in a protrusion on the head that frequently becomes damaged as a result of impact forces received at the protrusion during normal operation. Also, existing torch designs with a head protrusion have increased size and weight that limits an operator""s ability to easily and accurately maneuver the cutting torch, particularly in close working spaces.
Among the several objects of this invention may be noted the provision of a cutting torch which is relatively economical to manufacture; the provision of such a torch which is easy to assemble; the provision of such a torch which reduces maintenance; the provisions of such a torch which allows safe operation; the provision of such a torch which allows operation over an increased range of fuel pressures; the provision of such a torch which has a compact and lightweight torch head; and the provision of such a torch which is easy to maneuver in tight spaces.
In general, a torch of the present invention comprises a body including an oxygen preheat tube having a first longitudinal axis and a fuel gas preheat tube having a second longitudinal axis. A head is connected to the preheat tubes having an oxygen passage communicating with the oxygen preheat tube, a fuel gas passage communicating with the fuel gas preheat tube, and an outlet for the flow of mixed gases from the torch. A mixing chamber in the head communicates with the oxygen passage and fuel gas passage. The torch has an orifice in the oxygen passage through which oxygen is adapted to flow to the mixing chamber at an increased flow velocity with an accompanying pressure drop. The pressure drop assists in the flow of fuel gas into the mixing chamber for mixture with the oxygen. A diffuser in the head defines a diffuser passage having an inlet region for receiving oxygen and fuel gas from the mixing chamber for flow through the diffuser, and an outlet region for the delivery of oxygen and fuel gas to the outlet of the head. The oxygen passage and the diffuser passage are generally co-axial with the first longitudinal axis of the oxygen preheat tube.
In another aspect of the invention, a torch comprises a body including an oxygen preheat tube having a first longitudinal axis and a fuel gas preheat tube having a second longitudinal axis. A head is connected to the preheat tubes having an oxygen passage communicating with the oxygen preheat tube, a fuel gas passage communicating with the fuel gas preheat tube, and an outlet for the flow of mixed gases from the torch. A mixing chamber in the head communicates with the oxygen passage and fuel gas passage. A nozzle member received in the mixing chamber has an orifice through which oxygen is adapted to flow to the mixing chamber at an increased flow velocity with an accompanying pressure drop. The pressure drop assists in the flow of fuel gas into the mixing chamber for mixture with the oxygen. A diffuser in the head defines a diffuser passage having an inlet region for receiving oxygen and fuel gas from the mixing chamber for flow through the diffuser, and an outlet region for the delivery of oxygen and fuel gas to the outlet of the head. The nozzle member and the diffuser are non-removable from the head.
Other objects and features will be in part apparent and in part pointed out hereinafter.